Hybrid engine exhaust gas temperature control system

ABSTRACT

A power system is provided having a power source operationally coupled to a generator. The power system also includes an exhaust passage having at least one after-treatment device configured to release exhaust from the power source into the atmosphere. In addition, a controller is configured to determine at least one exhaust passage condition indicative of an exhaust temperature and operate the generator in response to the determination.

TECHNICAL FIELD

The present disclosure is directed to a hybrid engine and, moreparticularly, to a hybrid engine having the capability to control theexhaust gas temperature.

BACKGROUND

Hybrid engines typically include an electric motor and an internalcombustion engine. Internal combustion engines, including dieselengines, gasoline engines, natural gas engines, and other engines knownin the art may exhaust a complex mixture of air pollutants. The airpollutants are composed of solid particulate matter and gaseouscompounds including nitrogen oxides. Due to increased attention on theenvironment, exhaust emission standards have become more stringent, andthe amount of solid particulate matter and gaseous compounds emitted tothe atmosphere from an engine is regulated depending on the type ofengine, size of engine, and/or class of engine.

One method that has been implemented by engine manufacturers to complywith the regulation of these engine emissions includes the use ofafter-treatment devices such as nitrogen oxide absorbers, sulfur oxideabsorbers, and hydrocarbon catalysts. These devices operate by mixing achemical catalyst with exhaust gas produced by the engine to transformmuch of the existing pollutants into harmless elements such as water andnitrogen. However, these devices require a predetermined temperaturerange for efficient operation. In some situations, the temperature ofthe exhaust flowing through the after-treatment devices may be too lowfor efficient operation. Without raising the temperature in thesesituations, the exhaust exiting an engine may not meet the emissionregulations. In other situations, the overly high exhaust gastemperature may become hot enough to damage the after-treatment devices.

Several methods have been implemented to remedy this issue. One methodincludes using fuel burners or electric heaters to artificially raisethe temperature of the after-treatment devices to within thepredetermined efficiency range. Still, other methods include the use ofan air or liquid cooler to cool the temperature of the exhaust gas inorder to avoid damaging the after-treatment devices. While these methodsmay be effective, they can be inefficient, costly, and unreliable.

Yet another method that has been implemented is disclosed in U.S. Pat.No. 6,657,315, issued to Peters et al. (hereinafter the '315 patent).The '315 patent discloses a hybrid engine system including an internalcombustion engine and an electric motor. When the engine temperature isbelow a predetermined threshold, the electric motor provides a negativetorque to the internal combustion engine. By providing a negative torqueon the engine, the engine load increases which in turn, increases thetemperature of the exhaust gas passing through the after-treatmentdevices. When the engine temperature is above a predetermined threshold,an electric motor assists the internal combustion engine by providing apositive torque on the engine. By assisting the engine, the engine loaddecreases, which in turn decreases the exhaust gas temperature. The '315method eliminates the inefficiencies and cost of using additionalcomponents to control the temperature of the exhaust gas.

Although the method disclosed in the '315 patent may eliminate theinefficiencies and costs associated with using additional components tocontrol the exhaust gas temperature, the disclosed determination of thetemperature of the exhaust passing through the after-treatment devicesmay not be accurate. In particular, the method indirectly determines theexhaust gas temperature by sensing the temperature of the engine. Due toinefficiencies in the hybrid engine system, the temperature of theengine may not reflect the temperature of the exhaust gas passingthrough the after-treatment devices. Because of this, the '315 methodmay allow the exhaust gas temperature to be outside of the preferredtemperature range. This may lead to a reduction in the efficiency of theafter-treatment devices. It may also lead to heat-related damage to theafter-treatment devices.

The disclosed power system is directed to overcoming one or more of theproblems set forth above.

SUMMARY OF THE INVENTION

In one aspect, the present disclosure is directed toward a power system.The power system includes a power source operationally coupled to agenerator. The power system also includes an exhaust passage having atleast one after-treatment device and configured to release exhaust fromthe power source into the atmosphere. The power system further includesa controller configured to determine at least one exhaust passagecondition indicative of an exhaust temperature and operate the generatorin response to the determination.

Consistent with a further aspect of the disclosure, a method is alsoprovided for adjusting an exhaust gas temperature. The method includessensing at least one power source condition indicative of an exhaust gastemperature. The method also includes either applying an additional loadon a power source or assisting the power source in response to thesensed condition indicative of an exhaust gas temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic illustration of an exemplary disclosed machine;

FIG. 2 is a diagrammatic illustration of an exemplary disclosed powertrain for used with the machine of FIG. 1; and

FIG. 3 is a flow chart depicting an exemplary method of operating thepower train of FIG. 2.

DETAILED DESCRIPTION

FIG. 1 illustrates an exemplary machine 10 having multiple systems andcomponents that cooperate to accomplish a task. The tasks performed bymachine 10 may be associated with a particular industry such as mining,construction, farming, transportation, power generation, or any otherindustry known in the art. For example, machine 10 may embody a mobileor stationary machine such as the on-highway vocational vehicle depictedin FIG. 1, a bus, an off-highway haul truck, a generator, or any othertype of mobile or stationary machine known in the art. Machine 10 mayinclude one or more traction devices 12 operatively connected to anddriven by a power train 14.

Traction devices 12 may embody wheels located on each side of machine 10(only one side shown). Alternatively, traction devices 12 may includetracks, belts or other known traction devices. It is contemplated thatany combination of the wheels on machine 10 may be driven and/orsteered.

Power train 14 may be an integral package configured to generate andtransmit power to traction devices 12, hydraulic pumps (not shown) foran excavator (not shown), or any other device requiring power from apower source. In particular, power train 14 may include a power source16, which may be operably associated with a generator 18 and may drivegenerator 18 such that mechanical energy from power source 16 isconverted into electric energy. Power train 14 may also include a motor20 connected to receive power output from generator 18 and transmit thepower output in a useful manner to traction devices 12. As shown in FIG.2, power train 14 may further include a power storage device 22, whichmay store electrical energy produced by generator 18 or supply storedelectrical energy to motor 20. Additionally, the components of powertrain 14 may be in communication with and controlled by a controller 24.It should be understood that, in an alternate embodiment, power train 14may include a hydraulic pump (not shown), hydraulic motors (not shown),and an accumulator (not shown). It should also be understood that, in analternate embodiment, power train 14 may include a flywheel (not shown)for storing energy.

Additionally, power source 16 may include an internal combustion enginehaving multiple subsystems that cooperate to produce mechanical orelectrical power output. For the purposes of this disclosure, powersource 16 is depicted and described as a four-stroke diesel engine. Oneskilled in the art will recognize, however, that power source 16 may beany other type of internal combustion engine such as, for example, agasoline or a gaseous fuel-powered engine. One of the subsystemsincluded within power source 16 may be an exhaust system 26. Othersubsystems included within power source 16 may be, for example, a fuelsystem, an air induction system, a lubrication system, a cooling system,or any other appropriate system (not shown).

Exhaust system 26 may remove or reduce the amount of pollutants in theexhaust produced by power source 16 and release the treated exhaust intothe atmosphere. Exhaust system 26 may include an exhaust passage 28which may be in fluid communication with an exhaust manifold 30 of powersource 16. Exhaust system 26 may also include after-treatment devicesfluidly connected along exhaust passage 28 such as a particulate filter32 and/or a catalytic device 34.

Particulate filter 32 may be any general type of exhaust filter known inthe art. Particulate filter 32 may include any type of filter media (notshown) known in the art, such as, for example, a ceramic foam, ceramic,sintered metal, metal foam, or silicon carbide, or silicon carbide foamtype filter. The filter media (not shown) may assist in removingparticulate matter like soot, soluble organic fraction (SOF), and otherpollutants produced by power source 16. The filter media (not shown) maybe situated horizontally, vertically, radially, or in any otherconfiguration allowing for proper filtration. Additionally, the filtermedia (not shown) may be of a honeycomb, mesh, mat, or any otherconfiguration that provides an appropriate surface area available forfiltering of particulate matter. Furthermore, the filter media (notshown) may contain pores, cavities or spaces of a size that allowsexhaust gas to flow through while substantially restricting the passageof particulate matter. In an alternate embodiment, the filter media (notshown) may contain heating elements capable of heating the filter media(not shown) and the exhaust during a regeneration process.

Catalytic device 34 may be disposed downstream of particulate filter 32,and may include components that function to treat exhaust as it flowsfrom particulate filter 32. Specifically, exhaust emissions nowsubstantially free of particulate matter may flow from particulatefilter 32 through a catalyst medium (not shown) that is retained withina housing of catalytic device 34. It is contemplated that one or morecatalyst mediums may alternatively be arranged to receive the gaseousemissions in series or parallel relation. The number of catalyst mediumswithin catalytic device 34 may be variable and depend on the backpressure, filtration, and size requirements of a particular application.It is contemplated that catalytic device 34 may alternatively be locatedupstream of particulate filter 32.

The catalyst medium may include, for example, a foam material having acatalyst configured to react with the exhaust flow entering catalyticdevice 34. The foam material may be formed from sintered metallicparticles such as, for example, alumina, titania, or any otherhigh-temperature alloy. The foam material may also be formed fromceramic particles such as, for example, silicon carbide, cordierite,mullite, or any other ceramic particles known in the art. The foammaterial may be formed into a filter medium through a casting process,an injection molding process, or any other process that produces aporous material with a desired porosity. A catalyst may be incorporatedthroughout the foam material and may be configured to reduce an amountof nitrogen oxide in the flow of exhaust, to decrease an oxidationtemperature of the particulate matter trapped by the particulatefiltration medium, to reduce an amount of carbon monoxide in the flow ofexhaust, and/or to reduce an amount of unburned hydrocarbons in the flowof exhaust. The catalyst may include, for example, an oxidationcatalyst, an SCR catalyst, an HC-DeNOx catalyst, or any otherappropriate type of catalyst. It is contemplated that the catalystmedium may alternatively include a wire mesh material having a catalystcoating. It is further contemplated that catalytic device 34 may beomitted, if desired, and a catalyst coating applied to particulatefilter 32.

Catalytic devices operate efficiently only within a certain temperaturerange. In addition, critical functions involving after-treatment devicessuch as the regeneration of particulate filter 32, require that theexhaust gas be above a threshold temperature. In order to monitor thetemperature of the exhaust gas flowing through the after-treatmentdevices, a sensor 36 may be associated with exhaust passage 28 to sensea temperature of the exhaust gas. Sensor 36 may be any type oftemperature sensor mounted within exhaust passage 28. For example,sensor 36 may embody a surface-type temperature sensor that measures awall temperature of exhaust passage 28. Alternately, sensor 36 may be agas-type temperature sensor that directly measures the temperature ofthe exhaust gas within exhaust passage 28. Sensor 36 may generate anexhaust gas temperature signal and send this signal to controller 24 viaa communication line (not shown) as is known in the art. Thistemperature signal may be sent continuously, on a periodic basis, oronly when prompted to do so by controller 24.

In an alternate embodiment, it is contemplated that controller 24 mayutilize other sensory input as a substitute for the temperature signal,if desired. Such input may be associated with various exhaust passageparameters, such as, for example, exhaust gas flow rate, exhaust gaspressure, or any other parameter known in the art. Controller 24 mayreceive and analyze this input to derive the exhaust gas temperature.

Generator 18 may be any known AC or DC generator such as, permanentmagnet, induction, switched-reluctance, or a hybrid combination of theabove, and may also be sealed, brushless, and/or liquid cooled, forexample, to provide a more durable design. Generator 18 may beoperatively coupled to power source 16 via a crankshaft, or in any othermanner known in the art, and may be configured to convert at least aportion of a power output of power source 16 to electrical energy. In anexemplary embodiment, generator 18 may be configured to both drive powersource 16 and be driven by power source 16. In addition, generator 18may be used to provide electric energy to power one or more electricmotors 20. It may be contemplated that generator 18 can be configured toproduce a direct current (DC) output or an alternating current (AC)output. It is also contemplated that AC or DC outputs may be convertedwith the use of a power converter (not shown) to produce a variety ofcurrent and/or voltage outputs for use by various components of machine10.

Electric motor 20 may be operatively coupled to generator 18 andconfigured to provide a mechanical force for performing a taskassociated with machine 10. Electric motor 20 may be any known AC or DCmotor such as, permanent magnet, induction, switched-reluctance, or ahybrid combination of the above, and may also be sealed, brushless,and/or liquid cooled. Although referred to in the singular, electricmotor 20 may be more than one electric motor. By virtue of receivingelectric energy from generator 18 and/or power storage device 22,electric motor 20 may create a torque for driving traction devices 12.Although electric motor 20 is illustrated as a drive for one or moretraction devices 12, it is contemplated that electric motor 20 may beused in any application of machine 10 that may require mechanical energyto operate.

Power storage device 22 may be any kind of known power storage devicesuch as, for example, a battery and/or an ultra-capacitor, or flywheel.In an exemplary embodiment, power storage device 22 may store excesselectric energy generated by generator 18 and/or provide any additionalelectric energy that may be needed when starting machine 10 and/orduring operation of machine 10. For example, when machine 10 isoperating in a low load condition, for example, it is neither travelingacross the ground nor operating any of its implements (not shown), powersource 16 may continue to run at a given engine speed or engine speedrange. In such relatively low load conditions, it may be possible tooperate machine 10 more efficiently, for example, and generator 18 cancontinue to convert mechanical energy into electric energy, which may bestored in power storage device 22. Alternatively, for a situation inwhich machine 10 is traveling across the ground at a given speed, andthe operator commands a work implement to perform a task such as, forexample, the operator commands a bucket containing a load of dirt to beraised while machine 10 remains moving, power storage device 22 mayprovide additional energy beyond the electric energy being generated bygenerator 18, and may prevent the engine from lugging down or stalling,and/or may prevent machine 10 from slowing down.

In addition to powering motor 20, both generator 18 and power storagedevice 22 may be used to power electric power consuming devices 38.Electric power consuming devices 38 may include, for example, one ormore of an air conditioning unit, a heating unit, a resistive grid,lights, appliances, personal electronics, pumps, motors, and otherelectronic engine components and accessories known in the art.

Controller 24 may embody a single microprocessor or multiplemicroprocessors that include a means for controlling the operation ofpower train 14. Numerous commercially available microprocessors can beconfigured to perform the functions of controller 24. It should beappreciated that controller 24 could readily embody a general machinemicroprocessor capable of controlling numerous machine functions or anengine microprocessor. Controller 24 may include a memory, a secondarystorage device, a processor, and any other components for running anapplication. Various other circuits may be associated with controller 24such as power supply circuitry, signal conditioning circuitry, solenoiddriver circuitry, and other types of circuitry.

INDUSTRIAL APPLICABILITY

The disclosed exhaust treatment system may provide a reliable andinexpensive way to control the exhaust temperature in a hybrid enginesystem. In particular, the disclosed exhaust treatment system mayeliminate the need for inefficient, expensive, and unreliable peripheraldevices by adjusting the engine load to produce the desired exhausttemperature necessary for the proper function of the after-treatmentdevices. The operation of the exhaust treatment system will now beexplained.

As is illustrated by the method disclosed in FIG. 3, at step 100, sensor36 may sense the temperature of the exhaust gas in exhaust passage 28.Sensor 36 may then transmit signals based on the exhaust gas temperatureto controller 24. At step 102, controller 24 may receive the signalsfrom sensor 36 and may determine whether the exhaust gas temperature isbelow a first predetermined threshold, e.g., 200 degrees Celsius.Controller 24 may make this determination by performing algorithms,referencing a look-up map, or follow other techniques well-known in theart.

Step 104 may be performed if controller 24 determines that the exhaustgas temperature is below the first predetermined threshold. During step104, controller 24 may cause generator 18 to convert the kinetic energyproduced by the spinning of the crankshaft (not referenced) of engine 16into electric energy. When converting kinetic energy to electric energy,generator 18 may develop a resistive torque. The resistive torque worksagainst the torque produced by engine 16 and ultimately adds to theexisting load placed on engine 16. Applying the additional load onengine 16 requires engine 16 to increase fueling. The increased fuelingmay result in an increased exhaust temperature. It should be understoodthat if generator 18 is already applying a load on engine 16, then theload may be increased to raise the exhaust temperature.

By applying the load on engine 16, generator 18 may produce excesselectrical energy. In step 106, generator 18 may distribute the excesselectrical energy in one of a number of ways. For example, generator 18may direct the excess electrical energy to battery 22. Charging battery22 may be the most efficient use of the excess electrical energy becausethe excess energy produced by engine 16 can be stored for later use.However, if battery 22 is already fully charged, the excess electricalenergy may be used to operate electrically actuated accessories 38. Suchaccessories may include an air conditioner, an electrically driven fanor pump, or any other electrically actuated device known in the art. Ifit is not preferred to operate electrically actuated devices, andbattery 22 is fully charged, the excess electrical energy may bedissipated through a resistive grid (not shown).

Once generator 18 has begun applying the load to engine 16, step 108 maybe performed. At step 108, sensor 36 may sense the temperature of theexhaust gas in exhaust passage 28. Sensor 36 may then transmit signalsbased on the exhaust gas temperature to controller 24. At step 110,controller 24 may receive the signals from sensor 36 and may determinewhether the exhaust gas temperature is still below the firstpredetermined threshold. Controller 24 may make this determination byperforming algorithms, referencing a look-up map, or follow othertechniques well-known in the art.

If controller 24 determines that the exhaust temperature is still belowthe first predetermined threshold, then generator 18 may continueapplying the load. However, if controller 24 determines that the exhausttemperature is above the first threshold temperature, then step 112 maybe performed. At step 112, generator 18 terminates the additional load.It should be understood that if generator 18 was applying a load toengine 16 before the disclosed method was performed, then the load maynot be terminated. Instead, the load may be reduced to the level appliedbefore the commencement of the disclosed method.

Step 114 may be performed after step 112 is accomplished or ifcontroller 24 determines that the exhaust temperature is above the firstpredetermined threshold. At step 114, controller 24 may receive thesignals from sensor 36 and may determine whether the exhaust gastemperature is above a second predetermined threshold, e.g., 600 degreesCelsius. Controller 24 may make this determination by performingalgorithms, referencing a look-up map, or follow other techniqueswell-known in the art.

If controller 24 determines that the exhaust temperature is below thesecond predetermined threshold, then sensor 36 may continue to sense theexhaust gas temperature. However, if controller 24 determines that theexhaust temperature is above the second predetermined threshold, thenstep 116 may be performed.

At step 116, controller 24 may cause battery 22 to assist engine 16 inpowering vehicle 10. By using the electrical energy stored in battery 22to help power vehicle 10, the load applied to engine 16 is reduced.Reducing the load on engine 16 allows engine 16 to reduce fueling. Thereduced fueling may result in a decreased exhaust temperature. It shouldbe understood that if battery 22 is already assisting engine 16 powervehicle 10, then the electrical energy supplied by battery 22 may beincreased to lower the exhaust temperature.

Once battery 22 has begun supplying electrical energy, step 118 may beperformed. At step 118, sensor 36 may sense the temperature of theexhaust gas in exhaust passage 28. Sensor 36 may then transmit signalsbased on the exhaust gas temperature to controller 24. At step 120,controller 24 may receive the signals from sensor 36 and may determinewhether the exhaust gas temperature is still above the secondpredetermined threshold. Controller 24 may make this determination byperforming algorithms, referencing a look-up map, or follow othertechniques well-known in the art.

If controller 24 determines that the exhaust temperature is still abovethe second predetermined threshold, then battery 22 may continuesupplying the electrical energy stored in battery 22. However, ifcontroller 24 determines that the exhaust temperature is below thesecond threshold temperature, then step 122 may be performed. At step122, battery 22 may discontinue the supply of electrical energy. Itshould be understood that if battery 22 was supplying electrical energybefore the disclosed method was performed, then the amount of electricalenergy may be reduced to the level being supplied before thecommencement of the disclosed method.

Using the generator to apply an additional load on the engine or usingthe battery to assist the engine when the exhaust temperature is outsideof the optimal range of the after-treatment devices provides anefficient, cost effective, and reliable method for complying withexhaust emissions regulations. Specifically, a significant portion ofthe energy produced when increasing the exhaust temperature can beharnessed rather than wasted by storing it in the battery for later usewhen the engine exhaust needs to be cooled. In addition, theconfiguration of the system does not require additional components thatmight add to the complexity and cost of the system. Furthermore, becausethe controller reacts to the actual temperature of the exhaust when itflows through the after-treatment devices, the system provides areliable and accurate means to control the temperature of the exhaust.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the disclosed system withoutdeparting from the scope of the disclosure. Other embodiments will beapparent to those skilled in the art from consideration of thespecification disclosed herein. It is intended that the specificationand examples be considered as exemplary only, with a true scope beingindicated by the following claims and their equivalents.

1. A power system, comprising: a power source operationally coupled to agenerator; an exhaust passage including at least one after-treatmentdevice and configured to release exhaust from the power source into theatmosphere; and a controller configured to determine at least oneexhaust passage condition indicative of an exhaust gas temperature andoperate the generator in response to the determination.
 2. The powersystem of claim 1, further including a sensor located in the exhaustpassage and configured to measure a temperature of the exhaust, whereinthe controller is in communication with the sensor to receive atemperature signal.
 3. The power system of claim 2, wherein thecontroller is configured to operate the generator in a manner thatapplies an additional load on the power source when the signal indicatesthe temperature of the exhaust gas being below a first thresholdtemperature.
 4. The power system of claim 3, wherein the first thresholdtemperature is approximately 200 degrees Celsius.
 5. The power system ofclaim 2, further including a power storage device, wherein thecontroller is configured to operate the power storage device in a mannerthat assists the power source when the signal indicates the temperatureof the exhaust gas being above a second threshold temperature.
 6. Thepower system of claim 5, wherein the second threshold temperature isapproximately 600 degrees Celsius.
 7. The exhaust treatment system ofclaim 1, further including a sensor configured to sense anon-temperature parameter of the exhaust passage and generate aparameter signal indicative of the non-temperature parameter, whereinthe controller is in communication with the sensor and is configured toderive the exhaust gas temperature value from the parameter signal. 8.The exhaust treatment system of claim 7, wherein the controller isconfigured to operate the generator in a manner that applies anadditional load on the power source when the signal indicates thetemperature of the exhaust gas being below a first thresholdtemperature.
 9. The exhaust treatment system of claim 8, furtherincluding a power storage device, wherein the controller is configuredto operate the power storage device in a manner that assists the powersource when the signal indicates the temperature of the exhaust gasbeing above a second threshold temperature.
 10. A method for adjustingan exhaust gas temperature, comprising: sensing at least one powersource condition indicative of an exhaust gas temperature; and eitherapplying an additional load on a power source or assisting the powersource in response to the sensed condition indicative of the exhaust gastemperature.
 11. The method of claim 10, wherein applying the additionalload on the power source further includes applying the additional loadon the power source when the temperature of the exhaust gas is below afirst threshold temperature.
 12. The method of claim 11, wherein thefirst threshold temperature is approximately 200 degrees Celsius. 13.The method of claim 11, further including storing electrical powerproduced by the application of the additional load on the power source.14. The method of claim 11, further including operating electricaldevices with excess electricity produced by the application of theadditional load on the power source.
 15. The method of claim 10, whereinassisting the power source further includes assisting the power sourcewhen the temperature of the exhaust gas is above a second thresholdtemperature.
 16. The method of claim 15, wherein the second thresholdtemperature is approximately 600 degrees Celsius.
 17. A method foradjusting an exhaust temperature in a hybrid engine, comprising:determining the temperature of an exhaust gas; determining whether thetemperature is within a predetermined temperature range; applying anadditional load on an engine when the exhaust temperature is below thepredetermined temperature range; and assisting the engine when theexhaust temperature is above the predetermined temperature range. 18.The method of claim 17, further including storing electrical powerproduced by the application of the additional load on the engine. 19.The method of claim 17, further including operating electricalaccessories with excess electricity produced by the application of theadditional load on the engine.
 20. The method of claim 17, furtherincluding discontinuing the application of the additional load on theengine or discontinuing the assistance to the engine when the exhausttemperature is within the predetermined temperature range.